1. Field of the Invention
The present invention relates generally to catheters and, more particularly, is directed to a catheter of the type having its distal end adapted to be anchored in a body cavity.
2. Description of the Prior Art
With catheters of the type adapted to be inserted into the urinary bladder and retained therein, it is generally desirable to construct the catheter tube with as small an outer diameter as possible so as to reduce discomfort to the patient during insertion, use and withdrawal. One type of catheter which has conventionally been used includes a main fluid passage through which the urine flows and a smaller parallel fluid passage which extends to an inflatable retention balloon molded as an integral part of the inlet end portion of the catheter. However, such "balloon" type catheters generally require a relatively large diameter with the attendant discomfort to the patient.
It has therefore been proposed, as shown, for example, in U.S. Pat. No. 2,649,092, to provide a single fluid passage or tubular portion having a series of longitudinally extending slits extending along the tubular portion adjacent its distal end. A wire is attached to the distal end of the tubular portion and, when pulled towards the proximal end, causes the strands of the tubular portion to extend outwardly so as to anchor the distal end in the bladder. At such time, urine flows through the slits into the tubular portion and out of the catheter.
Such prior catheters have generally been formed with at least three slits of equal length for anchoring the distal end thereof in the bladder. However, the use of three or more slits may not provide the catheter with a satisfactory anchoring characteristic. This is because the width of each strand is decreased as the number of strands increases. Further, although this type of catheter generally has a smaller outer diameter than that of the "balloon" type catheters, the outer diameter cannot be made too small without further reducing the width of the strands. For example, in the slitted catheters employed heretofore it was difficult to reduce the outer diameter of the catheter below about 4 mm, which still resulted in substantial discomfort to the patient and for small children rendered the catheter extremely difficult if not impossible to use.
It is also desirable to provide good drainage from the bladder to the catheter tube. In this regard, the above known catheters having three or more slits probably provide satisfactory drainage, wherein the urine is passed through the slits into the catheter tube. However, if only one slit is provided, unsatisfactory drainage may result, particularly in the case where solid or partially solid elements in the urine block the one slit.